1. Field of the Invention
This invention relates to optical apparatus such as photographic cameras and more particularly to apparatus especially adapted to electronic control for moving an element in such a camera.
2. Description of the Problem
The recent trend in the control of photographic cameras is toward the use of microprocessors as general purpose programmed logic control elements. As this trend continues, more and more of the features previously provided by mechanical linkages are being provided by electromechanical transducers. Some of the resulting advantages are lower costs, higher reliability, and greater versatility. Even the most advanced electronically controlled cameras today still contain a considerable amount of mechanical complexity. FIG. 1 of U.S. Pat. No. 4,086,581 issued Apr. 25, 1978 to Ito et al, provides an excellent illustration of the profusion of gears and levers used to move some elements in even the most highly evolved computer controlled cameras of today. One of the elements moved by mechanical linkages is the reflex viewing mirror in a single lens reflex camera. Other moveable elements could include, for example, close-up lens elements, or filter elements. As shown in FIG. 1 of the '581 patent, the viewing mirror is controlled by a complex train of levers and springs, first set in motion by an electrical signal applied to a solenoid.
Briefly, the function of the mirror control apparatus is to pivot the viewing mirror out of the optical path of the camera just prior to each exposure, and to return the mirror to the viewing position at the completion of exposure. It would be desirable to accomplish this function electronically, under control of the logic control element of the camera with a minimum of mechanical complexity. The problem faced by the inventor, therefore, was to provide an electromechanical transducer for reliably moving an element such as the reflex mirror in optical apparatus such as a single lens reflex camera, while avoiding the mechanical complexity of the prior art actuating mechanisms.